D&D motor question

[mrphilf]

I am running that motor with a GE 500a controller and 22" tires with 8v Trojans. I'm getting 17mph on flat grass. I have a lot of torque but it takes a ton of battery too. Still tracking down possible electrical issues but I drop below 42v way too often on hills. I did stand it up a couple weekends ago on a small but very steep incline.

Per Vic at D&D he said it would do 14mph but I'm obviously exceeding that

[northwestfarmtn]

Originally Posted by mrphilf

I am running that motor with a GE 500a controller and 22" tires with 8v Trojans. I'm getting 17mph on flat grass. I have a lot of torque but it takes a ton of battery too. Still tracking down possible electrical issues but I drop below 42v way too often on hills. I did stand it up a couple weekends ago on a small but very steep incline.

Per Vic at D&D he said it would do 14mph but I'm obviously exceeding that

I have one and it does 14 on flat road at 36v 22" aggressive treads, it gets to 12mph quick and if you have a couple hundred feet it will hit 14.1.

[scottyb]

Very good motor for off roaders and hunters. It produces the highest torque output for this cart. It will run on 36 or 48 v with a 500a control, 2g cables, and HD F&R.

[ghs819]

Going to look today to see what controller is in cart, it has that motor, and a newer fnr switch and controller. needs batteries, and a lot of other work...

[ghs819]

Has lift, now I need a donor parts cart

[mrphilf]

I would like to interject and recommend Scottys reversing contactors. I have already melted down a HD FNR switch, changed it to the contactors last week and gained 2mph :)

[JohnnieB]

Originally Posted by mrphilf

I am running that motor with a GE 500a controller and 22" tires with 8v Trojans. I'm getting 17mph on flat grass. I have a lot of torque but it takes a ton of battery too. Still tracking down possible electrical issues but I drop below 42v way too often on hills. I did stand it up a couple weekends ago on a small but very steep incline.

Per Vic at D&D he said it would do 14mph but I'm obviously exceeding that

That is a lot of motor, a lot of controller and a lot of tire height, so the problem is likely to be: Not enough energy stored in the battery pack.

Voltage drop under load is determined by number on Amps being drawn and AH stored in the battery.
AH stored is determined by the battery's rated storage capacity and its SoC (State of Charge) at the time.

In other words, the voltage of a battery pack at 75% SoC will drop further under load then the same battery pack at 100% SoC with the same load.

Taking the 48V pack below to 42V (1.75VPC) isn't instantly destructive, but avoid taking it below 36V (1.50VPC), that is where lead starts getting sucked off the plates.

Which model 8V Trojan batteries are you running?

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Vic's estimates of how fast the motors he designs will propel a cart, seem to be a bit on the conservative side.

He tells me my motor shouldn't be pushing my cart at 28+ MPH on 18.3" tires with a 42V battery pack. Ironically, I later discovered my tire height is only 17" rather than the 18.3" I thought it was, so at 28.5 MPH (GPS) the motor is spinning at 7k rather than the 6.5k we thought it was spinning at.

[options89]

I'm running it, with 27's it will lift the front end easily, I run around 30mph flat with my setup. I had to dial the controller ramping way down for safeties sake

[mrphilf]

I'm running T-875's and a DPI Accusense charger. My run time is awesome, IMO, I can run the thing in the mountains fully loaded for 3+ hours and still be around 85+% SOC .

I haven't stalled the motor or come close to it even pulling hills that are a little scary steep and loaded but my voltage really drops. It seems to drop a little less since I have switched to Scotty's super duty reversing contacts after melting down a HD FNR. Part of that change was also rewiring the cart a bit, Scotty's diagram didn't match how my cart was wired, so I had 2 changes at once, but those 2 changes resulted in a solid 2mph (GPS) gain and seems to have decreased the voltage drop and increased the run time but its too early to gauge how much of either. I need to make a new set of 2ga wires because of both the rewire changing the lengths and also the terminals on my new batteries are on the opposite sides than my old ones were. Not to mention I heated a couple of them up pretty bad when I melted down the FNR...so I will concede that they are a part of my problem now. However I ran it pretty hard the last 2 nights, in fact I broke a front leaf last night and I stopped several times to take temp readings and the highest any of the wires got was 103, not great but they can't be costing me that much power if thats all the hotter they got.

With my SOC at 90-100% I will consistently drop below 42v on long steep hills to the point that I slow down to like walking speed to keep the voltage above 42 as much as possible since I have read so much on here about hurting the batteries. Sometimes I even stop the cart on the hill for a minute or so to let the SOC recover a bit, really don't like doing that. If I kept my foot to the floor I would probably still stay above 40v or high 39s at the absolute worst but I'm hesitant to based on what I have read here.

Now if you are telling me that running the pack at 39.8v (random pick of a number) for a minute or 2 straight isn't going to hurt anything...well then I just got a whole lot happier with my build because this has bugged me to the point of thinking of selling my almost brand new 6 8v's and buying 8 6v's instead

[JohnnieB]

Originally Posted by mrphilf

.................Now if you are telling me that running the pack at 39.8v (random pick of a number) for a minute or 2 straight isn't going to hurt anything...well then I just got a whole lot happier with my build because this has bugged me to the point of thinking of selling my almost brand new 6 8v's and buying 8 6v's instead

You're probably shortening their usable lifespan a little, but other than that, I don't believe you aren't hurting them as long as you stay above 1.50 VPC (36V for a 48V pack).

They are a little lightweight for your application, so it would be a good idea to replace them with T-890 or Ranger 160 batteries when they expire.

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You mentioned that you are running the cart at night (cooler air temp) and the 2ga cables got to 103°F, and you also mention you gained about 2 MPH when you replaced the F/R switch with a reversing contactor, which also appeared reduced the voltage drop. That tells me some of the voltage drop is occurring outside the batteries and there might be some room for more improvement in the amp delivery system.

A set of 2Ga cables shouldn't get much more than about 10°F above the ambient air temperature and all 13 cables should be close to the same temperature. The motor housing can and will get very hot (up to 239°F is Max safe limit), so the cable connections on the motor studs will be a little hotter then the rest of the connections.

If possible, monitor the voltage of single batteries with a DVM while under load and compare it the the total pack voltage at the time. Each should be about 1/6 of the total pack voltage. If not, you are loosing voltage in the high current cables and connections.

You can also check for cables losses on the five cables connecting the six batteries in series while the batteries are being charged. When the DPI is putting out about 17A, measure the voltage drop across each of the cables connect the batteries together. If it is much more than 0.003V per foot, the cable needs to be repaired/replaced. (You can check the other cables by substituting them for the ones in the battery pack.)